The overall objectives of these investigations are to define more precisely the manner in which immunologic reactions cause damage to the cornea, and to relate these immunopathologic events to problems of clinical importance. The model system employed is that of the graft-versus-host destruction of rabbit corneal endothelium by sensitized lymphocytes introduced into the anterior chamber. The mechanism of lymphocyte-target cell interaction and the cellular requirements for this destructive process will be examined. Parallel studies will be performed in vitro in corneal endothelial tissue cultures, using both the transplantation system and a model in which a viral infection of the endothelial cell renders it susceptible to the action of anti-virus sensitized lymphocytes. An attempt will also be made to employ the production of the polypeptide secretory component of immunoglobulin A as a functional marker for a study of the metaplasia of conjunctival to corneal epithelium.